Push-pull electric switch



Oct. 31, 1967 D. A. OLSON 3,350,522

PUSH-PULL ELECTRIC SWITCH Filed Sept. 2, 1966 2 Sheets-Sheet 2 /0 3g "2/6 III I I A 5! {IL J' l I'IIIIIHIB 4 l9 l-l# lag i R P1 .6

2 W l I I [1'3 INVENTOR. DAV/0 ,4. 0450 BY fiwwww wed e, I

Patented Oct. 31, 1967 3,350,522 PUSH-PULL ELECTRIC SWITCH David A.Olson, Ridgway, Pa., assignor to Stackpole Carbon Company, St. Marys,Pa., a corporation of Pennsylvania Filed Sept. 2, 1966, Ser. No. 577,0239 Claims. (Ci. 200-76) This invention relates to push-pull electricswitches of the general type shown in Drcssel Patent No. 2,947,832.

It is among the objects of this invention to provide such a switch whichhas a more positive snap action, which is easy to assemble, in which thecontact pressure increases before the switch is snapped open when theswitch is cycled from On to Off, and in which there is a wiping actionbetween the contacts as the switch is being opened and closed.

In accordance with this invention, a carrier extending across the insideof a switch housing is connected to the rear end of a longitudinallymovable control shaft which moves the carrier back and forth. A switcharm extends across the rear end of the shaft between the carrier and theback wall of the housing and is norm-ally inclined to the shaft. One endof the arm is pivotally connected to one end of the carrier on an axissubstantially parallel to the back of the housing to permit the oppositefree end of the arm to be swung forward and backward. A coil spring iscompressed between the free end portion of the arm and a portion of thecarrier that is spaced lengthwise of the carrier from the end to whichthe arm is pivotally connected. This spring normally is inclined to thearm to hold the free end of the arm in either its front or backposition. The free end of the arm extends forward past the carrier intoengagement with the front wall of the switch housing when the carrier isin its rear position. When the carrier is in its front position, anelectric contact carried by the arm engages a fixed contact in thehousing mounted on its back wall. The carrier is movable by the shaftfrom either of its two positions to the other far enough to move thecarrier-engaging ends of the arm and spring past the point where thelongitudinal axes of the arm and spring are in alignment, so that thespring thereupon can snap the free end of the arm in the directionopposite to the direction of the movement of the carrier.

The preferred embodiment of the invention is illustrated in theaccompanying drawings, in which FIG. 1 is a plan view;

FIG. 2 is a mainly longitudinal section taken on the line II-II of FIG.1 showing the switch closed;

FIG. 3 is an enlarged cross section taken on the line III-III of FIG. 2;

FIG. 4 is a cross section taken on the line IVIV of FIG. 2;

FIG. 5 is an enlarged fragmentary side view with the switch housingshown in section and the switch open;

FIG. 6 is a view from the right-hand side of FIG. 3, with a portion ofthe switch housing broken away; and

FIGS. 7 and 8 are enlarged perspective views of the carrier and switcharm, respectively.

Referring to the drawings, principally FIG. 2, a control shaft 1 isrotatably and slidably mounted in a bushing 2 secured to the front of asuiable volume control unit 3. The bushing is threaded and adapted toextend through a hole in a mounting panel and to receive a nut forrigidly mounting the bushing in place. The shaft has a non-circular rearportion 4 that is splined in a head 5 of insulating material rotatablymounted in the volume control housing. The head carries the usual springcontact 6 that slidingly engages a resistance element 7 in the volumecontrol unit. The rear end of the shaft extends back through a centralopening 8 in the back of the volume control and into a switch housing 9,which may be made of an insulating material. The back of the volumecontrol housing forms the front wall of the switch housing, which isprovided with a back wall parallel to the front wall. The switch housingalso has an integral side wall. The switch housing may be connected tothe volume control housing in various ways, one way being by cars 10struck out of the control housing and bent into notches 11 in the sideof the switch housing.

Inside of the switch housing there is a carrier 13 (FIG. 7) made ofinsulating material and extending across the housing. This carrier,which is somewhat like a bar, has tongues 14 and 15 on its opposite endsthat slide in grooves 16 in the adjoining side wall of the housing sothat the carrier can move back and forth in the housing in a straightline only. For producing this movement of the carrier, the front of itis provided centrally with an integral boss 17 having a T-shape slot 18in it extending from side to side in the carrier. A headed connectingmember 19 is rotatably mounted in this slot and joined to the rear endof the shaft, preferably integrally. Consequently, the shaft can beturned in the carrier and can also move the carrier back and forth inthe switch housing. The carrier also is provided with a large rearwardlyopening recess 20 formed by the rearwardly extending end portions of thecarrier that engage the back wall of the switch housing when the carrieris in its rear position shown in FIG. 5. When it is in its frontposition (FIG. 2) the main front surface of the carrier engages thefront wall of the switch housing, with the boss 17 extending through thecentral opening 8 therein.

A pair of parallel electric terminals 22 in back of the switch housingextend forward through its back wall, from which they project forward ashort distance to form electric contacts 23. In order to engage thefixed contacts, one or more movable contacts are provided. A singlebridging contact 24 for engaging both fixed contacts simultaneously isshown. This bridging contact is carried by an arm 25 (FIG. 8) that isformed from a plate of insulating material. In either its On (FIG. 2) orits 01f (FIG. 5) position the arm is inclined to the control shaft andextends across it in carrier recess 20. One end of the arm, the outerend, is pivot-ally connected to the carrier on an axis that issubstantially parallel to the back wall of the switch housing so thatthe inner or free end of the arm can be swung back and forth.

The preferred way of making this pivotal connection is to provide theinner surface of the adjoining rearwardly projecting end portion of thecarrier with a notch or notches 27 extending transversely thereof, andto round the outer end of the arm so that it can rock in the notches.The arm is wider than the carrier and its outer end is bifurcated inorder to straddle the end portion of the carrier as shown in FIG. 3 andthereby prevent the arm from moving transversely of the carrier. For thesame reason, the rear portion of the carrier can be provided with atongue 28 between the notches that projects into a notch 29 in the arm.

The free end of the arm has extensions 31 extending at right anglesthereto forward across the opposite sides of the carrier and intoengagement with the front wall of the switch housing when the free endof the arm is in its front position shown in FIG. 5. Between theseextensions the free end of the arm is spaced from the adjacent endportion of the carrier, and a coil spring 32 is compressed between them.The spring is held in place by tiny spherical nubs 33 and 34 integralwith the arm and carrier, respectively, and projecting into the oppositeends of the spring. As the free end of the arm is swung back and forth,the

ends of the spring can rock on these nubs. To facilitate such rockingand eliminate any tendency for the spring to bind on the nubs, the armand carrier are formed on opposite sides of the nubs with relativelysharp edges and 36 that engage the end loops of the spring on theirdiameters. Consequently, as the spring is swung back and forth it rockson these sharp edges.

It will be seen that when the switch is off, that is, when the carrieris in its rear position shown in FIG. 5, the arm and spring convergetoward the front of the housing and the arm extensions 31 are pressedagainst the front wall. The arm and spring thus are located principallyin the front part of the carrier recess. To turn on the switch, thecontrol shaft is pulled, which moves the carrier forward in the housing.However, the free end of the arm cannot move forward because itsextensions 31 already engage the front wall. During forward movement ofthe carrier the outer ends of the arm and spring are moved forward by itand past the point where the longitudinal axes of the arm and spring arein alignment. The spring is compressed as it and the arm are broughtinto line, but the moment their outer ends pass the alignment point thespring can start to expand and will snap the free end of the armbackward until the contact carried by it strikes the fixed contacts asshown in FIG. 2.

To open the switch, the control shaft is pushed. Since the free end ofthe switch arm cannot move backward with the carrier because ofengagement with the fixed contacts, the outer ends of the arm and springare moved backward past the point where the longitudinal axes of the armand spring are aligned, whereupon the compressed spring expands andswings the arm forward again. It will be noted that while the carrier ismoving backward and the spring therefore is being compressed, the coilspring causes the bridging contact to exert an increasing pressureagainst the fixed contacts until the moment the arm is snapped forward.There is no diminishing engagement and no arcing. Also, while the outerend of the arm is moving backward it causes the bridging contact toslide on the fixed contacts and this wiping engagement helps to keep thecontacts clean.

As the bridging contact 24 should engage flat against the fixed contactsat all times, the bridging contact is rather loosely mounted on theswitch arm. This can be done by making the bridging contact from a metalbar provided with a central projection engaging the back of the arm andalso provided with forwardly projecting end portions that extend throughnotches 38 in the edges of the arm. The front ends of the end portionsof the bar are increased in width to hold the bar in place, as shown inFIG. 5.

According to the provisions of the patent statutes, we have explainedthe principle of our invention and have illustrated and described whatwe now consider to represent its best embodiment. However, we desire tohave it understood that, within the scope of the appended claims, theinvention may be practiced otherwise than as specifically illustratedand described.

I claim:

1. A push-pull electric switch comprising a housing having front andback walls connected by a side wall, a fixed electric contact in thehousing mounted on the back wall, the front wall having a centralopening through it, a bushing rigidly mounted in front of the front wallin line with said opening, a control shaft slidably mounted in thebushing and extending back to said housing, a carrier extending acrossthe inside of the housing, means connecting the rear end of said shaftto the carrier for moving it back and forth when the shaft is pushed andpulled, a switch arm extending across the rear end of the shaft betweenthe carrier and the back wall of the housing and normally inclined tothe shaft, one end of the arm being pivotally connected to one end ofthe carrier on an axis substantially parallel to said back wall topermit the opposite free end of the arm to be swung forward andbackward, a coil spring compressed between the free end portion of thearm and a portion of the carrier spaced lengthwise of the carrier fromits said one end, the spring normally being inclined to the arm to holdsaid free end in either its front or back position, the free end of thearm extending forward past the carrier into engagement with said frontwall when the carrier is in its rear position, and an electric contactcarried by the arm and engaging said fixed contact when the carrier isin its front position, the carrier being movable by the shaft fromeither of said carrier positions to the other far enough to move thecarrier-engaging ends of said arm and spring past the point where thelongitudinal axes of the arm and spring are in alignment, whereby thespring can thereupon snap the free end of the arm in the directionopposite to the direction of movement of the carrier.

2. A push-pull electric switch as recited in claim 1, in which the endsof said carrier and the adjoining side wall of said housing are providedwith registering tongues and grooves for guiding the carrier forward andbackward in the housing, and said shaft-connecting means is rotatablyconnected to the carrier.

3. A push-pull electric switch as recited in claim 1, in which thecarrier has a rearwardly opening recess receiving said arm and spring,and said free end of the switch arm straddles the carrier at one end ofsaid recess when the carrier is in its rear position.

4. A push-pull electric switch as recited in claim 1, in which saidcarrier is notched for pivotally receiving said one end of the switcharm.

5. A push-pull electric switch as recited in claim 1, in which saidcarrier is provided with an edge parallel to said pivotal axis andengaging the adjoining end of the coil spring along a diameter thereof,and a spherical nub projects from said edge into the coil spring.

6. A push-pull electric switch as recited in claim 1, in which saidportion of the carrier is at the end thereof opposite its said one endand projects rearwardly, and said arm portion is spaced inwardly fromsaid carrier portion, whereby the arm and coil spring converge towardthe front wall when the carrier is in its rear position and the arm andspring converge toward the back wall when the carrier is in its frontposition.

7. A push-pull electric switch as recited in claim 6, in which theelectric contact carried by said switch arm is located between the coilspring and the pivoted end of the arm.

8. A push-pull electric switch as recited in claim 6, in which said oneend of the carrier projects rearwardly and is provided in its innersurface with a notch pivotally receiving said one end of the switch arm.

9. A push-pull electric switch as recited in claim 6, in which said oneend of the carrier projects rearwardly and is straddled by the pivotedend of the switch arm and is notched in its inner surface for receivingthe central portion of the pivoted end of the arm to provide the pivotalconnection.

References Cited UNITED STATES PATENTS 12/1956 Kommer 200--67 9/1966Schwartz 200-67

1. A PUSH-PULL ELECTRIC SWITCH COMPRISING A HOUSING HAVING FRONT ANDBACK WALLS CONNECTED BY A SIDE WALL, A FIXED ELECTRIC CONTACT IN THEHOUSING MOUNTED ON THE BACK WALL, THE FRONT WALL HAVING A CENTRALOPENING THROUGH IT, A BUSHING RIGIDLY MOUNTED IN FRONT OF THE FRONT WALLIN LINE WITH SAID OPENING, A CONTROL SHAFT SLIDABLY MOUNTED IN THEBUSHING AND EXTENDING BACK TO SAID HOUSING, A CARRIER EXTENDING ACROSSTHE INSIDE OF THE HOUSING, MEANS CONNECTING THE REAR END OF SAID SHAFTTO THE CARRIER FOR MOVING IT BACK AND FORTH WHEN THE SHAFT IS PUSHED ANDPULLED, A SWITCH ARM EXTENDING ACROSS THE REAR END OF THE SHAFT BETWEENTHE CARRIER AND THE BACK WALL OF THE HOUSING AND NORMALLY INCLINED TOTHE SHAFT, ONE END OF THE ARM BEING PIVOTALLY CONNECTED TO ONE END OFTHE CARRIER ON AN AXIS SUBSTANTIALLY PARALLEL TO SAID BACK WALL TOPERMIT THE OPPOSITE FREE END OF THE ARM TO BE SWUNG FORWARD ANDBACKWARD, A COIL SPRING COMPRESSED BETWEEN THE FREE END PORTION OF THEARM AND A PORTION OF THE CARRIER SPACED LENGTHWISE OF THE CARRIER FROMITS SAID ONE END, THE SPRING NORMALLY BEING INCLINED TO THE ARM AND TOHOLD SAID FREE END IN EITHER ITS FRONT OR BACK POSITION, THE FREE END OFTHE ARM EXTENDING FORWARD PAST THE CARRIER INTO ENGAGEMENT WITH SAIDFRONT WALL WHEN THE CARRIER IS IN ITS REAR POSITION, AND AN ELECTRICCONTACT CARRIED BY AN ARM AND ENGAGING SAID FIXED CONTACT WHEN THECARRIER IS IN ITS FRONT POSITION, THE CARRIER BEING MOVABLE BY THE SHAFTFROM EITHER OF SAID CARRIER POSITIONS TO THE OTHER FAR ENOUGH TO MOVETHE CARRIER-ENGAGING ENDS OF SAID ARM AND SPRING PAST THE POINT WHERETHE LONGITUDINAL AXES OF THE ARM AND SPRING ARE IN ALIGNMENT, WHEREBYTHE SPRING CAN THEREUPON SNAP THE FREE END OF THE ARM IN THE DIRECTIONOPPOSITE TO THE DIRECTION OF MOVEMENT OF THE CARRIER.